1. Field of the Invention
The present invention relates generally to a transport container with an interchangeable, bipartite inside container.
2. Description of the Related Art
Transport containers are used during the transportation of semiconductor wafers to protect the semiconductor wafers from contamination by ambient air which does not meet the highest cleanliness standards. For this reason, one of the most important properties of a transport container is its particle tightness.
There are number of possibilities for designing transport containers. For example, an especially simple design for a transport container is provided when the container is composed only of an outside hood, an outside bottom plate, and a semiconductor wafer holder. Another, more complicated structure is a transport container having an interchangeable inside container within which a semiconductor wafer holder is secured. A common feature to all such transport containers is that they have the same size and the same outside dimensions in order to be interchangeable with one another. They should also comply with certain standardized dimensions.
Standard dimensions for transport containers are recited, for example, in the publication document number 1332 of Semiconductor Equipment and Materials Institute, Inc., dated Jan. 10, 1986. The recommended standards are summarized under the term "standard mechanical interface for wafer cassette transfer" standard, also known as the SMIF standard. All of the most important dimensions of a transport container, as well as its essential outside component parts are recited in this publication. This publication also provides recommendations that the component parts of the transport container should meet.
The publication SMIF-Pod, "The Nucleus of the Asyst-SMIF system" of Asyst Technologies, Inc., discloses a transport container having an interchangeable inside container. The transport container is manufactured in accordance with the aforementioned SMIF specifications and is suitable for the acceptance of semiconductor wafers. In cross-sectional drawings, the details such as the inside hood semiconductor wafer holder, the outside hood, and the bottom plate of the transport container are shown being loaded with a semiconductor wafer cassette.
It is, of course, known to use transport containers for storing and transporting semiconductor wafers. Such transport containers are manufactured and distributed by various companies such as, for example, Asyst and Empak. Previous transport containers, however, involve either simple structures in which no inside containers are provided, or involve transport containers having inside containers that are not particle-tight. The demand made of the particle tightness of these transport containers is low, so that they can be utilized only in clean rooms with filtered ambient air. Another disadvantage of a simple structured transport container is that the transport container must be replaced and cleaned after a certain number of process steps in the semiconductor manufacturing process. When transport containers having inside containers are used, the contaminated inside container is replaced with a new one.